Darwin is a version of the BSD UNIX operating system that offersadvanced networking, services such as the Apache web server, and supportfor both Macintosh and UNIX file systems. It was originally released inMarch 1999. Darwin currently runs on PowerPC-based Macintosh computers,and is being ported to Intel processor-based computers and compatiblesystems by the Darwin community. Apple's open source projects allow developers to customize and enhancekey Apple software. Through the open source model, Apple engineers andthe open source community collaborate to create better, faster and morereliable products for our users. Beneath the appealing, easy-to-use interface of Mac OS X is a rock-solidfoundation that is engineered for stability, reliability, andperformance. This foundation is a core operating system commonly knownas Darwin. Darwin integrates a number of technologies, most importantlyMach 3.0, operating-system services based on 4.4BSD (Berkeley SoftwareDistribution), high-performance networking facilities, and support formultiple integrated file systems.